Abstract: The specific dynamics and thermodynamics characteristics of atmospheric motion near the ground are a result of the complex underlying surfacewhich affects the exchange process of matter and energy. The sandmeadow ecotone area of the Horqin sandy land is a typical region with complex terrain, and has unique eco-hydrological characteristics. At present, there are many laws to analyze flux by eddy covariance for the desert ecosystem, but the study for correction of eddy covariance flux is still very weak over the complex underlying surface in sandy land. Based on the observation data of July on mobile dune in Horqin Sandy Land, the paper firstly analyzed the changes of wind speed and the rotation angle of coordinate correction(β)which caused by terrain,then compared sensible and latent heat flux, the surface energy closure rate and data quality(the turbulence characteristics and wind friction velocity)corrected through Double rotation and Planar fit. Results show as follows:(1)In gentle topography area(200°-300°), vertical wind velocity(w)is over zero, and the average vertical wind velocity(W)is 0.163 m·s^-1; in steep topography area(330°-180°), w is less than 0, and W is -0.071 m·s^-1. (2) β corrected by Double rotation on gentle topography is around 1.677 3°;on steep topography,it is around -1.648 6° and has more concentrated dates. β corrected by Planar fit is around 0.2°.(3)Sensible heat fluxes(H)corrected by DR is in accord with measured value, while latent heat fluxes(LE)increasesby 17%. After corrected by PF, H and LE reduces by 4.5% and 15%, respectively. This indicates that both DR and PF have asignificant influence on LE. The R² of the correlation between H and corrected H, LE and corrected LE by DR are 0.988 2 and 0.870 8, respectively, which are both higher than thosecorrected by PF.(4)Analysis of data quality evaluation indexshow that there are 10.4% and 10.7% of the measure data of the turbulence characteristic beyond the scope of the theoretical value ±30%, after corrected by DR and PF. The consistency between measure data and theoretical value in steep topography area is poor. Wind friction velocity corrected by DR(R²=0.954)has higher correlation with the one before corrected(R²=0.933)than that corrected by PF(R²=0.933). The surface energy closure rate increases by 3.47% and 2.78% after corrected by DR and PF, respectively. Overall, the topography of mobile dune is quite uneven, plane fitted by planar fit cannot change with the variety of topography, therefore, for undulating mobile dunes, the performance of DR is better than PF.

Key words: mobile dune, eddy covariance, double rotation, planar fit, flux correction